Changed hydroboost unit

[N2BRK]

I did a ton of things to the truck in past few days, including an upgrade to my leaking hydroboost unit. I went to the new LML part.

I bled the unit by going back and forth lock to lock a million times, and I pumped the brake fully (engine off the whole time, and on the jack).

Driving felt great.

Then, engine running, I pushed the brake fully and held a couple times. After that my truck was pulling left and smelled like brakes. The brake fluid reservoir was way high and the fluid not so pretty. I sucked out the extra and went for a drive. All seems ok.

So... WTF? I’d love to know why this happened, please. Maybe there’s more to it that I should be concerned about. I’m going to flush the brake fluid tomorrow of course.

Thanks in advance!

 

[N2BRK]

FWIW - is considered that the brake could be dragging with the new hydro unit, but no brake light when I let off.

 

[mopar3]

Maybe you have a caliper or slide that's sticky? I can't think of any way the brake fluid level could be rising.

 

[N2BRK]

Maybe you have a caliper or slide that's sticky? I can't think of any way the brake fluid level could be rising.

I know, right! Crazy. I did not do a brake job either - just the hydroboost unit. And it only happened after a running full pedal press.

 

[TheBac]

Collapsed brake hose?

 

[N2BRK]

If so, then when I vacuum bleed tomorrow I should find one caliper not flowing, right? You think the new more powerful hydroboost damaged a weak line?

 

[mopar3]

You probably applied extra pressure and something hung up. Could be a pad slide, caliper. A bad hose will allow pressure in but not allow back to release. Jack up the wheels and stab the pedal a couple times and see if any brakes are dragging.

 

[N2BRK]

Thanks. I took a run to the parts store for brake fluid and made a few consecutive stops - not crazy just firm. After a couple the left front smoked some and I felt the abs.

Rotors, pads, slides, and bushings were done over the winter. Hoses are still OEM. I’ll take your advice on the jacking up and spinning etc., but I think as a matter of maintenance I’ll swap all hoses to stainless.

Do we have a vendor in the family here that does SS hoses?

 

[N2BRK]

Just a little more info - i jacked it up and took note of the effort to spin the wheels by hand. I took it out and made a few stops to heat up. I came back and jacked it up. More effort required for sure, on both sides. Levels in the master and hydroboost have not changed.

The new setup can lock the tires and engage the abs with a hell of a lot less effort. Wow.

 

[N2BRK]

Forgot to add - before I drove as above, I jacked it up and spun the wheels by hand. I stabbed the brake with the truck running several times and there was no change in effort to spin the wheels.

 

[N2BRK]

I don’t know if It’s fixed or what. I flushed in new brake fluid and went for about 20-25 stops and no problems at all. I can only hope/assume that there was some shit that blocked the return of fluid to the master, and I flushed it clean? Time will tell.